We use App_body because the architecture of the To-do is to load this template and dynamically load a child template that comes from the main property of the Template context.

The context of the Template is it's this.data that Blaze developers already familiar with, and we use it to pass the child Blaze Template we want to load (Lists_show_page) and the _id of the choosen list.

Great, now we are missing only one step to make it work.

The Lists_show_page Template (imports/ui/pages/lists-show-page.js) loads the ID of the list from the FlowRouter, and now it can load it from the this.data object, so let's change it: